If T is the type produced by a call to std::bind, this template provides the member constant value equal true. For any other type, value is false.

This template may be specialized for a user-defined type which should be treated by std::bind as if it was the type of a bind subexpression: when a bind-generated function object is invoked, a bound argument of this type will be invoked as a function object and will be given all the unbound arguments passed to the bind-generated object.